Bootstrap is a free and open-source framework for creating websites and web applications. It's the most popular HTML, CSS, and JS framework for developing responsive, mobile first projects on the web. As the web evolves more and more toward responsive design, it can be a real challenge for web developers to keep up. One of the main benefits of development frameworks like Bootstrap is that they can help speed up development times, while maintaining quality and consistency across the site. You no longer need to re-design every element. And you don't need to spend hours trying to get everything looking and working right across browsers, platforms, and devices. By using Bootstrap, all (most) of the hard work is done for you.